1. Field of Invention
This invention relates generally to chemically-bonded anchor studs for fastening fixtures and other objects to masonry, and more particularly to a centering sleeve and overflow ring assembly to facilitate the installation of the anchor stud in a hole drilled in masonry having deposited therein a flowable bonding agent which when cured anchors the stud in place.
2. Status of Prior Art
The term masonry refers to a construction of stone or similar material such as concrete and brick. The walls, ceiling and floors of many edifices are formed of masonry. In order, therefore, to fasten fixtures, machines, structural members or other objects to masonry, a masonry anchor is required for this purpose.
In the case of concrete or any other form of masonry, one cannot drill a hole therein and then tap this hole so that it can receive an anchor bolt, a threaded stud or other threaded mounting means to secure a fixture or other object to the face of the masonry. The nature of masonry is such that a tapping action to cut female threading into the bank of the hole cannot be effected, for this action will disintegrate the masonry material.
In order, therefore, to anchor a threaded rod or stud in a hole drilled in masonry, the present practice is to use a curable chemical bonding agent for this purpose. The typical agent of this type has two flowable components, one being a resinous bonding agent and the other, a hardener therefor. The resins may be phenol, vinyl, ester or epoxy based. The two components, when stored, must be separated to prevent interaction therebetween. Many bonding agents currently available have an accelerated curing time and set within 10 to 30 minutes to afford substantial holding power. In practice, a charge of the resinous component and sufficient hardener intermixed therewith is deposited in the hole, and a threaded mounting stud is then inserted in the hole.
To this end use may be made of a dispenser gun to inject a charge of the flowable bonding agent into the drilled hole. Or the charge may be contained in a capsule that is deposited in the drilled hole and is ruptured to release the bonding agent when the stud is inserted in the hole.
After the resinous interfacial layer between the stud and the bank of the hole cures and rigidifies, it then bonds itself both to the stud and to the masonry, so that the stud is permanently anchored in the hole. In order now to secure a fixture to the masonry face, the fixture which has a mounting hole therein is placed over and onto the projecting stud and locked thereto by a washer and nut.
Of prior art background interest is the Kellison U.S. Pat. No. 4,642,964 which discloses a fastening system for chemically-bonding an anchor bolt in a hole drilled in masonry.
One problem faced by the installer of an anchor stud or bolt into a hole drilled in masonry arises from the fact that when the hole has deposited therein a charge of an uncured bonding agent in which is inserted the anchor to be installed, the installer cannot then see into the hole. In order, therefore, to be sure that the charge of bonding agent he has deposited is adequate for its intended purpose, the installer depends on an overflow of the agent from the hole all around the anchor stud. This overflow indicates to the installer that the uncured bonding bonding agent in the hole is properly spread about the inserted anchor. However, while this overflow of uncured bonding agent is necessary to a proper anchor installation procedure, it also creates a multitude of problems, as will now be explained.
One ancillary problem encountered by an installer arises from the overflow of the uncured bonding agent onto the region of the masonry surrounding the projecting stud. While such overflow is useful, for it serves to indicate that the space surrounding the stud in the hole is filled with the uncured agent, this overflow onto the masonry surface cannot be permitted to cure and harden. Should this happen, a protuberance would be created on the masonry that would interfere with the proper placement of the fixture or other object onto the masonry.
Moreover, no matter how carefully the installer wipes off the uncured overflow, there is usually a residue left on the masonry surface. And when a fixture is then placed on this surface so that it can be fastened to the masonry, the residue at the interface of the fixture (or other object) will then bond the fixture to the masonry. This is highly undesireable, for should it be necessary to later remove the fixture from the masonry, it may then be very difficult to do so.
The stud inserted in the drilled hole has a diameter which is necessarily smaller than that of the drilled hole in order to create a space between the stud and the wall of the hole to accommodate the bonding agent. This gives rise to another serious problem, for the inserted stud is not held upright by the flowable uncured agent and tends to lean against the hole. As a consequence, the anchored stud projecting from the masonry will not be perpendicular to the surface of the masonry, and will not be properly aligned with the mounting hole in the fixture to be fastened to the masonry.
Since the diameter of the fixture mounting hole substantially matches that of the stud, a tilted stud may make it impossible to fasten the fixture to the masonry. In a typical installation, the fixture has at least four mounting holes, and these dictate a like number of anchor studs. Should any of these studs be inclined to a degree where it will not pass through the corresponding mounting hole in the fixture, one cannot then complete the installation.
When the stud is to be anchored in overhead masonry, so that the hole drilled therein has a vertical axis, or is to be anchored in vertical masonry so that the hole drilled therein has a horizontal axis, then still another problem is encountered. Now one is faced with leakage of the flowable bonding agent deposited in the hole as a result of gravity flow from the open end of the drilled hole.
Though the uncured agent is usually quite viscous and slow to leak out of the hole, a gradual leakage as a result of gravity flow will diminish the amount of agent in the annular space between the stud and the bank of the hole and may result in inadequate anchoring of the stud in the drilled hole. This may have serious consequences, especially in an overhead masonry installation to which a heavy object is fastened.
As evidenced by the Sawaide U.S. Pat. No. 5,049,015, it is known to fit a sleeve into the upper end of a hold bored in masonry in order to center the stud inserted through the sleeve into the hole which contains a charge of an uncured chemical bonding agent. The sleeve functions to maintain the stud upright while the agent undergoes curing. However, because the inner wall of the sleeve is in direct contact with the inserted stud, this blocks any overflow of the bonding agent out of the hole. As previously noted, such overflow is a useful indicator that the amount of agent in the hole is adequate to anchor the stud therein.
Also disclosing a centering sleeve fitted into the upper end of a masonry hole is the Fischer U.S. Pat. No. 4,211,049. The Fischer sleeve effectively closes the hole so that there is no outflow of binding material from the hole even when the hole is drilled in a ceiling or vertical wall.
An installation made in a hole drilled in overhead or vertical masonry presents a special problem for in both cases there is a possible loss of the bonding agent deposited in the hole as a result of gravity flow. When the stud is inserted in the drilled hole and plunged into the deposit of the flowable bonding agent, an overflow out of the hole is then desireable, for this is indicative of an adequate deposit to anchor the stud. To this end there must be a flow passage between the stud and the wall of the centering sleeve fitted into the hole.
However, after overflow takes place, the same flow passage will permit a viscous bonding agent to gradually leak out of the hole by reason of gravity flow and thereby diminish the amount of agent available to chemically anchor the stud in the hole.
Also of prior art interest is the Lang U.S. Pat. No. 4,263,132 which discloses a centering stud loosely received in a masonry hole and provided with an end flange that nests on the masonry.
The term stud, as used herein is used in a generic sense, and is applicable to any partially or fully threaded rod, bolt post or other rod-like member adapted to be anchored in masonry and to project therefrom.